The present invention relates to web in general, and more particularly to webs having a relief-structured surface and a pattern which is in register with the relief structure.
The invention also relates to a method of making such a web.
It is known to make multilayer polymer webs with relief-structured surfaces and patterns which are in registry with the structure, in a variety of ways. For example, foamed or unfoamed polymer panels can be printed with a desired pattern and thereupon be embossed. However, it is then difficult to obtain a registry of the printed pattern and the embossed pattern. A relatively large percentage of the production must be discarded as scrap. Moreover, the embossing effects on a finished polymer foil or on a foam layer are not permanent because the natural elasticity of the polymer materials results in a return to the original state, i.e. in an elimination of the embossment over a period of time.
Another proposal has been made in U.S. Pat. No. 2,964,799 according to which only those portions of a polymer web which are to be foamed, are embossed with a heating roller which heats them and causes them to foam. This is an improvement on the previous proposals, but it is still difficult to obtain a precise registry of the printed pattern and the embossed pattern. Methods of making chemical embossments have been proposed in Swiss Pat. No. 570,866, in French Pat. No. 1,270,669 and in the U.S. Pat. Nos. 3,293,094 and 3,293,108. In all of these cases a pre-gelled plastisol has printed on it, together with the desired pattern, one or more substances which influence the decomposition temperature of the blowing agent and which does regulate the foam formation. These substances may also cause the cross-linking of certain areas which are not to undergo foaming. The printing may be effected in accordance with known methods, preferably by intaglio printing. These proposals obtain a good registry between the printed pattern and the relief pattern. However, printing of pre-gelled plastisols is somewhat difficult because it is necessary to use solvent-containing inks which in turn requires the application of protective measures, such as the use of recovery installations and similar devices for toxicological and safety reasons. Then again, the selection of the type of solvent used is strictly limited because solvents which dissolve or cause substantial swelling of the plastisol surface would result in a destruction of the printed pattern. Another problem is that the colored print which can be obtained is also subject to limitations, because the degree of color saturation is limited when smooth non-absorbent surfaces--as in the case of pre-gelled plastisols--are being printed. In the one-color area of a printed pattern the surfaces show often an undesirable characteristic appearance, namely a mottled effect which results from the splitting of the ink layer between the plastisol surface and the surface of the printing roller, which splitting occurs as the printing roller and plastisol surface move apart. Still another problem is that these proposals are primarily limited to the use of the expensive intaglio printing process.